Thirty years ago, aliens arrive on Earth. Not to conquer or give aid, but to find refuge from their dying planet. Separated from humans in a South African area called District 9, the aliens are managed by Multi-National United, which is unconcerned with the aliens' welfare but will do anything to master their advanced technology. When a company field agent contracts a mysterious virus that begins to alter his DNA, there is only one place he can hide: District 9.

With only three weeks left in his three year contract, Sam Bell is getting anxious to finally return to Earth. He is the only occupant of a Moon-based manufacturing facility along with his computer and assistant, GERTY. When he has an accident however, he wakens to find that he is not alone.